Animals naturally develop a hierarchy amongst group members. This hierarchy becomes especially apparent when there is competition for food. When food is limited in a group sow house, low ranking sows often suffer from lack of food and this impacts their growth and reproductive abilities. This experiment examines the effects of social hierarchies and competitive feeding and how it impacts live weights and feeding behavior. The pigs were put into groups of twelve and either floor fed 3.0kgs/sow or fed a high fiber diet ad libitum. In order to determine social hierarchy the researchers put two sows in a pen and had them compete for a small feeder, it was recorded which sows were able to dominate over the others and after all pairings had been tested the sows were ranked in order of dominance. The sows social interactions were then observed by video camera for the weeks 2, 5, 9 and 13. It was noted where pigs would eat (left, middle or right side of the feeder), if there was other pigs at the feeder (0, 1, or 2), time spent at the feeder, how they approached the feeder (waiting for the feeder, displaced another pig or walked up to an empty spot), and finally how they left the feeder (voluntarily, displaced, or displaced another sow). In the pens with a feeder there was preference for the right side of the feeder but it was not determined why. Sows preferred to feed when there was no one else at the feeder, and almost never when there was 2 sows already at the feeder. Food was defended when there was food in the feeder, and during floor feeding. It was found that sows which weigh more were more likely to hold dominance over the others and when feeding was competitive in the floor feeding pens sows that weighed less were unable to eat as much and gained less weight. In the ad libitum feeding system lighter pigs were able to adjust their feeding habits to avoid confrontations and still attain sufficient nutrients.

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